Matlab is skipping over my while loop.

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Michael Garzarelli Garzarelli
回答： Stephen23 2020-2-15
I am trying to calculate the thurst, velocity, and displacement of an aircraft approaching takeoff. Matlab is skipping over my while loop and I do not know why. If i take the loop away there are no errors and will give me the answer "0" since that is what it would be with no iterations. If you could please help it would be greatly appreciated.
Code:
%Question 2
clc, clear
%Constants
b=36;
Sw=175;
Hw=5.7;
AR=b^2/Sw;
e=2/((2-AR)+sqrt(4+AR^2));
AReff=AR*sqrt(b/(2*5.7));
CDG=(.65*4)^2/(3.14*e*AReff);
%Part A
CD=CDG+.02+.018
%Part B
T0=765;
rho=.002377;
Wto=3500;
Pmax=270;
g=32.2;
muroll=.023;
Dprop=84/12;
Clmax=4;
CLG=.65*Clmax;
deltat=.01;
Tguess=700;
Vcr=110;
Vstall=64.8;
V=1.2*Vstall;
n=1;
t(n)=0;
x(n)=0;
V(n)=0;
a(n)=0;
T=Groundroll(T0,V);
T(n)=T;
while V(n)<V
n=n+1;
T(n)=Groundroll(T0,V(n));
t(n)=t(n-1)+deltat;
V(n)=V(n-1)+a(n-1)*deltat;
q(n)=.5*V(n)^2*rho;
Daero(n)=CDG*q(n)*Sw;
L(n)=CLG*q(n)*Sw;
Droll(n)=muroll*(Wto-L(n));
Fx(n)=T(n)-Daero(n)-Droll(n);
a(n)=g*(Fx(n)/Wto);
x(n)=x(n-1)+.5*(V(n)+V(n-1))*deltat;
x=x(n)
V=V(n)
end

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回答（1 个）

Stephen23
Stephen23 2020-2-15
"Matlab is skipping over my while loop and I do not know why."
Because you told it to.
Lets have a look at what values V and n have before the loop runs:
>> V
V = 0
>> n
n = 1
Now lets look at your loop condition... But first, is zero less than zero? (hint: no). We can check that using MATLAB too:
>> V(n)<V
ans = 0
Ergo your condition is not true, and the loop never runs. Because that is exactly what you told MATLAB to do.

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